Eudora 7.1 and gmx: I can't send messages anymore?

[i***@jejejeje.it]

Hello, for a while now I can't send messages with my gmx account. I
also tried changing the Serrver to "SMTP Server", but I still can't
send messages.
Does anyone know why? I'm attaching 2 photos of the problem and the
Eudora 7.1 configuration.
Thanks,
Jones
Loading Image...
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[i***@jejejeje.it]

If I choose "Alternate port" Eudora is able to send messages but then
I get this error:

This message was created automatically by mail delivery software.

A message that you sent could not be delivered to one or more of
its recipients. This is a permanent error.

The following address failed:

alvoììì***@tin.it:
SMTP error from remote server for GREETING command, host:
mx.tin.it (34.90.152.141) reason: 550 mail not accepted from
blacklisted IP address [212.227.17.20]

[John B. Smith]

Post by i***@jejejeje.it
If I choose "Alternate port" Eudora is able to send messages but then
This message was created automatically by mail delivery software.
A message that you sent could not be delivered to one or more of
its recipients. This is a permanent error.
mx.tin.it (34.90.152.141) reason: 550 mail not accepted from
blacklisted IP address [212.227.17.20]

My ISP (Spectrum cable) somehow shut off all sending of email by any
email client I could find. I can still download email with Eudora in
xp. Eudora never quite worked in Win7, though I find other uses for it
there. I eventually gave up trying and go to Spectrum's inconvenient
site when I have to send email. Don't think I ever attempted Eudora in
Win10. Never saw a discussion of this problem but I suspect it exists
everywhere. ISPs hate email clients.